The pencil hardness test is one method for measuring the hardness of a material’s surface.
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What is the Pencil Hardness Test?
The pencil hardness test is a method for evaluating the surface hardness of a coating by scratching it with pencils of varying hardness grades and determining the hardest grade that does not scratch the surface.
Defined in JIS K 5600-5-4 “Testing methods for paints — Scratch hardness (Pencil method),” it is widely used as a simple and inexpensive test method.
JIS K 5600-5-4 Overview
JIS K 5600-5-4 specifies the test method for evaluating the scratch hardness of paint coatings using pencils. The key test conditions are as follows:
- Pencil hardness grades: 6B (softest) to 9H (hardest), 17 grades total
- Test load: 750 g ± 10 g
- Test angle: 45° to the specimen surface
- Test speed: 0.5–1.0 mm/s
- Stroke: Approximately 7 mm
The evaluation result is expressed as the hardest pencil grade that does not produce a scratch. For example, if a “3H” pencil does not scratch the surface but a “4H” pencil does, the pencil hardness is reported as “3H.”
Advantages and Disadvantages of the Pencil Hardness Test
Advantages
- Simple and low-cost: Ordinary commercially available pencils are used, so initial equipment investment is minimal.
- Widely adopted: Standardized by JIS and ISO, the method is widely recognized in the industry.
- Fast evaluation: Results can be obtained quickly compared with other surface hardness test methods.
Disadvantages
- Reproducibility concerns: The pencil tip changes shape during testing, which can affect the results. Results may also vary depending on the pencil manufacturer.
- Limited scope: Primarily intended for paint coatings; not optimal for evaluating plastic films or other materials. (JIS K 7317:2022 is recommended for functional films.)
- Subjective judgment: Determining whether a scratch occurred relies on visual assessment, introducing some variability.
HEIDON Pencil Hardness Tester: TYPE:38
HEIDON’s TYPE:38 is a pencil hardness tester compliant with JIS K 5600-5-4. It applies a constant load of 750 g and moves the pencil at a controlled speed, enabling stable and reproducible testing.
Surface Quality Measuring Machine TYPE:38
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HEIDON has been a leading friction and wear testing specialist since 1952. For customers who find purchasing a tester challenging, we also offer commissioned testing services.
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